Philips PM3055 Operation Manual page 29

3.3.3
3-15E
Horizontal deflection
This oscilloscope has a MAIN and a DELAYED time-base.
MAIN TIME—BASE (MTB)
The MTB is triggered on the signal selected in the TRIGGER SELECTOR stage.
Trigger selection can be made by the TRIG SOURCE or X softkey for:
A signal derived from channel A '
B signal derived from channel B
COMP composite triggering of both channels A and B
EXT external input via BNC socket
LINE signal derived from mains (line) voltage
Positive or negative triggering is selected by the SLOPE softkey. A display of the trigger signal is made
possible by trigger view facility, if TRIG VIEW is selected by TRIG VIEW softkey.
This trigger signal can be displayed together with the input signal(s) of the selected vertical channel(s).
After selection of the source, selection of the MTB trigger mode or coupling can be made in the TRIGGER
AMPLIFIER. The TB TRIG MODE softkey allows selection of:
AUTO Automatic free run in the absence of trigger signals
TRIG Normal! triggering
SINGLE MTB sweep started once
The TRIG COUPL softkey allows selection of
PP Peak-to-peak triggering
DC Normal triggering
TVF Triggering on TV FIELD synchronisation pulses.
TVL Triggering on TV LINE synchronisation pulses.
The level at which the MTB starts is determined by adjustment of the LEVEL control.
The MAIN TIME—BASE GENERATOR determines the horizontal deflection coefficient via the MTB
s-s UP—DOWN control and the VAR control. The LCD displays the correct deflection simultaneously.
DELAYED TIME-—BASE (DTB)
Like the MTB, the DTB is routed via the DTB TRIGGER SELECTION, TRIGGER AMPLIFIER and
DELAYED TIME—BASE GENERATOR.
When STARTS is selected by the DTB TRIG softkey, the COMPARATOR compares the MTB sawtooth
with the adjustable delay time and gives a trigger signal to the DELAYED TIME BASE GENERATOR. This
delay time is selected by the DTM up-down control.
The HORIZONTAL SELECTION stage selects the horizontal deflection source by the TB SELECT softkey
or the X DEFL softkey.
The following deflection sources are possible:
MTB MTB sawtooth only
MTBI ; MTB and intensified part of DTB
MTBI + DTB See MTBI, plus DTB sawtooth
DTB DTB sawtooth only
X DEFL Deflection by signal selected by TRIG SOURCE or X softkey.
The selected horizontal deflection signal is fed to the FINAL HORIZONTAL AMPLIFIER.
The TB MAGN softkey enables the horizontal deflection coefficient to be magnified by a factor of 10.
Horizontal shift of the trace is achieved by the X POS control.
The FINAL HORIZONTAL AMPLIFIER drives the horizontal deflection plates (X) of the CRT.